Solid-state imaging device, method for driving solid-state imaging device, and imaging apparatus

ABSTRACT

A solid-state imaging device includes an imaging unit, a charge control unit, and a horizontal transfer unit. The imaging unit includes a plurality of pixels arranged into a matrix for performing photoelectric conversion, and a plurality of vertical transfer units arranged in columns for vertically transferring signal charges of the plurality of pixels on a column-by-column basis. In a predetermined operation mode, a predetermined number of columns greater than one are used as a unit, and the charge control unit stops transferring charges from a vertical transfer unit in a predetermined column of the predetermined number of columns, and adds the signal charges transferred from the vertical transfer units in the two or more remaining columns of the predetermined number of columns to output the added signal charges. The horizontal transfer unit horizontally transfers the signal charges output from the charge control unit.

RELATED APPLICATION DATA

This application is a continuation of U.S. patent application Ser. No.11/256,996, filed Oct. 24, 2005, the entirety of which is incorporatedherein by reference to the extent permitted by law. The presentapplication claims priority to Japanese Patent Application No.2004-315490 filed in the Japanese Patent Office on Oct. 29, 2004, theentirety of which also is incorporated by reference herein to the extentpermitted by law.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to solid-state imaging devices, methodsfor driving solid-state imaging devices, and imaging apparatuses. Morespecifically, the present invention relates to a charge-transfersolid-state imaging device, such as a charge-coupled-device (CCD)imaging device, a method for driving the solid-state imaging device, andan imaging apparatus, such as a digital still camera, including thecharge-transfer solid-state imaging device as an imaging device.

2. Description of the Related Art

Imaging apparatuses, e.g., digital still cameras (DSCs), includeall-pixel-readout solid-state imaging devices, such as CCD imagingdevices, as imaging devices. In the all-pixel-readout solid-stateimaging devices, signal charges of all pixels that are simultaneouslyread out to vertical transfer units are vertically transferredindividually, rather than jointly, by the vertical transfer units, andare horizontally transferred and output by a horizontal transfer unit.The number of pixels in CCD imaging devices for DSCs has increased inorder to increase the still image quality.

In CCD imaging devices including multiple pixels, smearing due tohigher-density cells (or unit pixels) is conspicuous, and, inparticular, is conspicuous in a moving-image capturing mode or amonitoring mode. Smearing is a phenomenon unique to CCD imaging devicesin which vertical bright stripes appear in high-brightness areas of animage of an object when bright light enters vertical transfer units fortransferring signal charges. The longer the signal charges remain in thevertical transfer units, the more conspicuous the smearing effect is.

The frame interline transfer (FIT) method that is used in professionalbroadcast CCD imaging devices is one solution for reducing theoccurrence of smearing. In FIT-type CCD imaging devices, alight-shielded accumulator for temporarily accumulating signal chargestransferred by vertical transfer units is provided below an imaging unitincluding a matrix of pixels. The signal charges are read out from thepixels to the vertical transfer units, and are then rapidly transferredto the accumulator by the vertical transfer units performing ahigh-speed transfer operation. The period of time during which thesignal charges remain in the vertical transfer units is reduced, therebyreducing the occurrence of smearing.

However, such FIT-type CCD imaging devices with accumulators lead to alarge chip size, which is about 1.5 to 2 times as large as the chip sizeof CCD imaging devices of the interline transfer (IT) type withoutaccumulators. In view of cost, therefore, it is difficult to useFIT-type CCD imaging devices as imaging devices in consumer imagingapparatuses, such as digital still cameras.

While the VGA quality (640 pixels wide by 480 pixels high) is suitablefor the DSC video function, demands for DSC CCD imaging devicesincluding a large number of pixels have increased in order to increasethe still image quality. With the demands for CCD imaging devicesincluding more pixels, an increased number of pixels lead to a large gapbetween the frame rate in a still-image capturing mode and the framerate used for the vide function (including monitoring).

One known implementation of the video function is a technique forthinning out signal charges read out from pixels in the verticaldirection to increase the frame rate. For example, referring to FIG. 12,in color coding of two (horizontal) by two (vertical) pixel patterns,two pixels of each color for every 16 vertical pixels (16 lines) areread out to vertical transfer units and added in the vertical transferunits, and the signal charges of the remaining pixels are not read out(or are thinned out) (4/16-line readout).

In the vertical thinning-out and addition operation, signal charges offour pixels for every 16 pixels are read out to the vertical transferunits, and signal charges of 12 pixels are not read out, that is, 12pixels are thinned out. In the vertical transfer units, packets of theread out signal charges (a packet is the unit in which charges arehandled) and empty packets of the unread signal charges include smearcomponents, and the smear components are added by charge transfer. Thus,although the signal components are thinned out, the number of smearcomponents increases, and the occurrence of smearing increases.

Due to a high thinning-out rate, or a large number of pixels beingthinned out, information regarding the thinned out pixels is notreflected in the final captured image, and false-color signals or moiréartifacts are caused. In addition, the amount of horizontal pixelinformation is excessively larger than the amount of vertical pixelinformation, which is uneconomical, and there is no balance between thevertical resolution and the horizontal resolution.

In the related art, the number of vertical pixels to be thinned out isreduced to increase the amount of pixel information, thereby preventingthe occurrence of smearing or the generation of false-color signals.Furthermore, in order to prevent the horizontal driving frequency (thedriving frequency of the horizontal transfer unit) from increasing dueto an increased amount of pixel information, pixel addition is alsoperformed in the horizontal direction to reduce the amount of pixelinformation (see, for example, Japanese Unexamined Patent ApplicationPublication No. 11-234569).

For example, referring to FIG. 13, in color coding of two (horizontal)by two (vertical) pixel patterns, two pixels of each color for everyeight vertical pixels (eight lines) are read out to vertical transferunits and added in the vertical transfer units (4/8-line readout), andtwo pixels of each color in the horizontal direction are added in ahorizontal transfer unit. The number of pixels from which signal chargesare not read out is therefore reduced to one third compared with4/16-line readout, thereby reducing the occurrence of smearing or thegeneration of false-color signals.

SUMMARY OF THE INVENTION

The above-described technique of the related art can reduce theoccurrence of smearing and the generation of false-color signals byincreasing the amount of vertical pixel information using a combinationof thinning-out and addition in the vertical direction and two-pixeladdition in the horizontal direction, and can prevent the horizontaldriving frequency from increasing by reducing the amount of horizontalpixel information. However, the amount of horizontal pixel informationcan only be reduced to ½ while the amount of vertical pixel informationis reduced to ¼. That is, the amount of horizontal pixel information istwo times as large as the amount of vertical pixel information, and theproblem of no balance between the vertical resolution and the horizontalresolution still remains.

It may be possible to reduce the amount of horizontal pixel informationby using the thinning-out and addition operation in the vertical andhorizontal directions. In the related art, however, since thethinning-out and addition operation is carried out in charge transferunits, as discussed above, the smear components included in the emptypackets are added by charge transfer, and the number of smear componentsincreases although the signal components are thinned out, and theoccurrence of smearing increases.

A solid-state imaging device according to an embodiment of the presentinvention includes a plurality of pixels arranged into a matrix forperforming photoelectric conversion and a plurality of vertical transferunits arranged in columns for vertically transferring signal charges ofthe plurality of pixels on a column-by-column basis, and a horizontaltransfer unit for horizontally transferring the signal chargestransferred from the plurality of vertical transfer units. In apredetermined operation mode, a predetermined number of columns greaterthan one are used as a unit, transfer of charges from a verticaltransfer unit in a predetermined column of the predetermined number ofcolumns is stopped, and the signal charges transferred from the verticaltransfer units in the remaining columns of the predetermined number ofcolumns are added or read out to output the added or read out signalcharges.

In the solid-state imaging device with the above-described configurationor an imaging apparatus including the solid-state imaging device as animaging device, when a predetermined operation mode is set, transfer ofcharges from a vertical transfer unit in a predetermined column of apredetermined number of columns greater than one that are used as a unitis stopped, and the signal charges transferred from the verticaltransfer units in the remaining columns are added or read out to outputthe added or read out signal charges, thereby performing thethinning-out and addition or thinning-out and read-out processing in thehorizontal direction. That is, with respect to the column for whichtransfer of charges is stopped, pixel information is thinned out.

The number of pixels to be thinned out or the number of pixels to beadded can arbitrarily be set depending on the number of pixels to bethinned and added in the vertical direction to provide a good balancebetween the vertical resolution and the horizontal resolution and toreduce the horizontal driving frequency. Furthermore, transfer ofcharges of the vertical transfer unit in the column of which pixels areto be thinned out is stopped, thereby allowing the signal components andthe smear components to be thinned out. No empty packets including onlysmear components are produced in the horizontal transfer unit, thuspreventing the occurrence of smearing.

According to an embodiment of the present invention, in units of aplurality of columns of a plurality of vertical transfer units, transferof charges from a vertical transfer unit in a predetermined column ofthe plurality of columns is stopped, and the signal charges transferredfrom the vertical transfer units in the remaining columns are added orread out to output the added or read out signal charges. Thethinning-out and addition or thinning-output and read-out processingwithout the occurrence of smearing is performed in the horizontaldirection to reduce the amount of horizontal pixel information.Therefore, there is a good balance between the vertical resolution andthe horizontal resolution, and the horizontal driving frequency can bereduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram of an FIT-type CCD imagingdevice according to an embodiment of the present invention;

FIG. 2 is a schematic plan pattern view showing the configuration of themain part including a charge controller according to a first embodimentof the present invention;

FIG. 3 is a conceptual diagram showing vertical pixel addition in thefirst embodiment;

FIG. 4 is a timing chart showing the operation of the charge controlleraccording to the first embodiment in a moving-image capturing mode;

FIG. 5 is a conceptual diagram showing vertical addition and horizontalthinning-out and addition in units of three pixels in both vertical andhorizontal directions, by way of example;

FIG. 6 is a timing chart showing the operation of the charge controlleraccording to the first embodiment in a still-image capturing mode;

FIG. 7 is a plan view pattern view showing the configuration of the mainpart including a charge controller according to a second embodiment ofthe present invention;

FIG. 8 is a conceptual diagram showing vertical pixel addition in thesecond embodiment;

FIG. 9 is a timing chart showing the operation of the charge controlleraccording to the second embodiment in a moving-image capturing mode;

FIG. 10 is a timing chart showing the operation of the charge controlleraccording to the second embodiment in a still-image capturing mode;

FIG. 11 is a block diagram showing an example configuration of animaging apparatus according to an embodiment of the present invention;

FIG. 12 is a conceptual diagram to illustrate a problem with the relatedart; and

FIG. 13 is a conceptual diagram to illustrate another problem with therelated art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will now be described in detailwith reference to the drawings.

FIG. 1 is a schematic configuration diagram showing the configuration ofa charge-transfer solid-state imaging device according to an embodimentof the present invention, e.g., a CCD imaging device 10. The CCD imagingdevice 10 shown in FIG. 1 has an FIT-type device configurationincluding, for example, an imaging unit 11 and an accumulator 12.

Referring to FIG. 1, the imaging unit 11 includes a matrix of pixels(photosensors including photoelectric conversion devices) 111 forconverting incident light into signal charges of an amount correspondingto the amount of the incident light, and a plurality of vertical CCDs(vertical transfer units) 112 each provided for a column of pixels inthe matrix of pixels 111. The signal charges photoelectrically convertedby the pixels 111 and read out from the pixels 111 are verticallytransferred on a column-by-column basis by the vertical CCDs.

According to an embodiment of the present invention, a charge controller13 is provided between the imaging unit 11 and the accumulator 12. Thespecific configuration and operation of the charge controller 13 arediscussed in detail below in the context of two embodiments.

The accumulator 12 is a region shielded from light, and is used fortemporarily accumulating the signal charges supplied via the chargecontroller 13. The vertical CCDs 112 and the charge controller 13 aredriven to perform a high-speed transfer operation, and the signalcharges are rapidly transferred to the accumulator 12 from the verticalCCDs 112 and the charge controller 13.

As is known in the art, the FIT-type CCD imaging device 10 including theaccumulator 12 can reduce the period of time during which the signalcharges remain in the vertical CCDs 112, and is therefore greatlyeffective to reduce the occurrence of smearing.

The signal charges temporarily accumulated in the accumulator 12 aresequentially shifted (or transferred) to a horizontal CCD (horizontaltransfer unit) 14. The horizontal CCD 14 horizontally transfers thesignal charges shifted from the accumulator 12. The CCD imaging device10 further includes a charge detecting unit 15 at the leading end of thehorizontal CCD 14. The charge detecting unit 15 includes, for example,floating-diffusion amplifiers, and is adapted to convert the signalcharges sequentially transferred by the horizontal CCD 14 into voltagesignals and to output the signals from a port CCDout.

The CCD imaging device 10 with the above-described configuration isdriven by various timing signals generated by a timing generator (TG)20. Based on a vertical synchronization signal VD, a horizontalsynchronization signal HD, and a master clock MCK, the timing generator20 generates timing signals including, for example, six-phase verticaltransfer pulses IM1 to IM6 for driving the vertical CCDs 112, storagepulses Storage1 and Storage2 and hold pulses Hold1 and Hold2 for drivingthe charge controller 13, for example, four-phase vertical transferpulses ST1 to ST4 for driving the accumulator 12, for example, two-phasehorizontal transfer pulses H1 and H2 for driving the horizontal CCD 14.These timing signals are generated so as to have the timing relationshipcorresponding to capturing mode information supplied from the outside.For example, a drain voltage Drain is supplied to the charge controller13 from the timing generator 20.

Configuration of Charge Controller

The specific configuration and operation of the charge controller 13will now be described in detail in the context of two embodiments.

First Embodiment

FIG. 2 is a schematic plan pattern view showing the configuration of themain part including a charge controller 13A according to a firstembodiment of the present invention. Color coding of a color filter (notshown) provided on the top layer of the imaging unit 11 is based on two(horizontal) by two (vertical) pixel patterns, by way of example, andthe charge controller 13A performs processing in units of three columns(i.e., three horizontal pixels).

In a predetermined operation mode, in units of a plurality of columns ofthe plurality of vertical CCDs 112, and the charge controller 13Aaccording to the first embodiment stops transferring charges from avertical CCD 112 in a predetermined column of the plurality of columnsto thin out the charges, and adds signal charges transferred from thetwo or more remaining vertical CCDs 112 to output the added signalcharges. This processing is hereinafter referred to as horizontalthinning-out and addition processing. In another operation modedifferent from the predetermined operation mode, the charge controller13A converts signal charges transferred in parallel from the verticalCCDs 112 in units of the plurality of columns into serially arrangedsignal charges, and sequentially outputs the serially arranged signalcharges.

Referring to FIG. 2, three vertical CCDs 112, namely, vertical CCDs112A, 112B, and 112C, are used as a unit. With respect to, for example,adjacent two vertical CCDs 112B and 112C in the three vertical CCDs112A, 112B, and 112C, the charge controller 13A is independentlyprovided with storage electrodes 131B and 131C and hold electrodes 132Band 132C in each of the channels in such a manner that the storageelectrodes 131B and 131C are closer to the imaging unit 11.

With respect to the remaining vertical CCD 112A, the charge controller13A is not provided with a storage electrode or a hold electrode. Withrespect to the middle vertical CCD 112B in the three vertical CCDs 112A,112B, and 112C, the storage electrode 131B is horizontally narrower (inwidth) than the storage electrode 131C, and a drain portion 133 servingas a charge drain unit is further provided in the lateral region of thestorage electrode 131B.

As discussed above, the charge controller 13A with the above-describedconfiguration is driven and controlled by the control pulses generatedby the timing generator 20, i.e., the storage pulses Storage1 andStorage2, the drain voltage Drain, and the hold pulses Hold1 and Hold2,to perform the horizontal thinning-out and addition processing.

Specifically, the storage pulse Storage1 is carried by a control line134-1 to drive the storage electrode 131B, and the storage pulseStorage2 is carried by a control line 134-2 to drive the storageelectrode 131C. The drain voltage Drain is carried by a control line134-3 to drive the drain portion 133. The hold pulse Hold1 is carried bya control line 134-4 to drive the hold electrode 132B, and the holdpulse Hold2 is carried by a control line 134-5 to drive the holdelectrode 132C.

For example, the control lines 134-1 to 134-5 carrying the storagepulses Storage1 and Storage2, the drain voltage Drain, and the holdpulses Hold1 and Hold2 extend in parallel to one another across thecharge controller 13A in the arrangement direction of the vertical CCDs112 (i.e., the horizontal direction), and have a shunt configurationsuch that the storage electrodes 131B and 131C, the drain portion 133,the hold electrodes 132B and 132C are brought into electrical contactfor every three columns.

That is, the storage electrode 131B and the hold electrode 132B providedfor the vertical CCD 112B are driven by a combination of the storagepulse Storage1 and the hold pulse Hold1, and the storage electrode 131Cand the hold electrode 132C provided for the vertical CCD 112C aredriven by a combination of the storage pulse Storage2 and the hold pulseHold2.

The imaging unit 11, the charge controller 13A, and the accumulator 12include channel stop regions 30, as hatched in FIG. 2.

The charge controller 13A with the above-described configurationperforms the horizontal thinning-out and addition processing in units ofthree columns (i.e., three horizontal pixels), by way of example, so asto support, for example, vertical three-pixel addition.

A method for driving the CCD imaging device 10 including the chargecontroller 13A with the above-described configuration will now bedescribed in the context of a moving-image capturing mode for capturinga moving image (including a monitoring mode) and a still-image capturingmode for capturing a still image.

Moving-Image Capturing Mode

First, the vertical pixel addition operation in the moving-imagecapturing mode will be described with reference to FIG. 3.

As an example, in a case of color coding based on a primary-color Bayerarray having two (horizontal) by two (vertical) pixel patterns,three-pixel addition in which three pixels of the same color are addedfor every other pixel is used, and the processing for thinning outpixels is not performed.

Addition of three pixels of the same color for every other pixel isperformed in the vertical direction without performing the thinning-outprocessing, thereby allowing for uniformity of the centroid of pixels intaking a moving image, as can be seen from equal intervals in thevertical direction between adders, indicated by typical signs in FIG. 3for adding pixels. No thinning-out of pixel information prevents thegeneration of false-color signals. In addition, since the processing forthinning out pixel information is not performed, no empty packets areproduced during vertical transfer, thus preventing the occurrence ofsmearing.

Now, the operation of the charge controller 13A in the moving-imagecapturing mode, that is, the horizontal thinning-out and additionoperation, will be described with reference to a timing chart shown inFIG. 4.

In the timing chart shown in FIG. 4, when the fifth-phase verticaltransfer pulse IM5 and then the sixth-phase vertical transfer pulse IM6are sequentially brought to a high level (hereinafter referred to as an“H” level) from a low level (hereinafter referred to as an “L” level),the vertical CCDs 112 (112A, 112B, and 112C) transfer the signal chargesof the pixels in the bottom row of the imaging unit 11 to the chargecontroller 13A. In units of three columns, i.e., the vertical CCDs 112A,112B, and 112C, the signal charges of the vertical CCD 112A in the firstcolumn are transferred to the accumulator 12, passing through the chargecontroller 13A.

The storage pulse Storage1 is in the “H” level state so that thepotential under the storage electrode 131B becomes deep, and the holdpulse Hold1 is in the “L” level state so that the potential under thehold electrode 132B becomes shallow. Thus, the signal charges of thevertical CCD 112B in the second column are accumulated under the storageelectrode 131B, and a potential barrier produced under the holdelectrode 132B stops transferring these signal charges to theaccumulator 12. The potential barrier stops transferring not only thesignal components (i.e., the signal charges) but also smear components(or smear charges). The accumulated charges over the potential barrierare drained to the drain portion 133 by the following vertical transferoperation.

The storage pulse Storage2 and the hold pulse Hold2 undergo a transitionfrom the “L” level to the “H” level in synchronization with the risingof the fifth-phase vertical transfer pulse IM5 so that the potentialunder the storage electrode 131C and the potential under the holdelectrode 132C become deep. Thus, as in the signal charges of thevertical CCD 112A in the first column, the signal charges of thevertical CCD 112C in the third column are transferred to the accumulator12, passing through the charge controller 13A.

Accordingly, in a case where the horizontal thinning-out and additionprocessing is performed in units of three columns, i.e., the verticalCCDs 112A, 112B, and 112C, the charge controller 13A stops transferringthe signal charges of the middle vertical CCD 112B, and transmits thesignal charges of the side vertical CCDs 112A and 112C so that thetransmitted signal charges are added in the accumulator 12. In themoving-image capturing mode, therefore, the charge controller 13A allowsthe horizontal thinning-out and addition processing for thinning out thepixel information (including the smear components) of the middle columnand adding the pixel information for the side columns.

In the first embodiment, when color coding of two (horizontal) by two(vertical) pixel patterns is carried out in units of three columns, asshown in FIG. 2, in a certain line, a signal charge of a green (G) pixelin a certain unit is thinned out and signal charges of blue (B) pixelson both sides of the G pixel are added, and a signal charge of a B pixelis thinned out in the adjacent unit and signal charges of B pixels onboth sides of the B pixel are added. In the next line, a signal chargeof a B pixel is thinned out in a certain unit and signal charges of Bpixels on both sides of the B pixel are added, and a signal charge of aG pixel is thinned out in the adjacent unit and signal charges of Bpixels on both sides of the G pixels are added.

The signal charges that are obtained by the charge controller 13Aperforming thinning-out to, for example, two third of the number ofhorizontal pixels, followed by addition, are vertically transferred tothe horizontal CCD 14 by the four-phase (ST1 to ST4) driving in theaccumulator 12. In the horizontal CCD 14, the signal charges arehorizontally transferred by the two-phase (H1 and H2) driving to thecharge detecting unit 15. The charge detecting unit 15 converts thesignal charges into voltage signals and outputs the converted signals.

In the capturing operation in the moving-image capturing mode,therefore, the horizontal thinning-out and addition processing isperformed, and the number of pixels to be added and the number of pixelsto be thinned out can arbitrarily be set depending on the number ofpixels to be added in the vertical direction to prevent the amount ofhorizontal image information from being excessively larger than theamount of vertical pixel information and to allow the same rate of pixelinformation in both directions. Therefore, there is a good balancebetween the horizontal resolution and the vertical resolution of amoving image. In the case of the first embodiment, in association withvertical three-pixel addition, one pixel is thinned out for every threehorizontal pixels. The amount of pixel information in the vertical andhorizontal directions is therefore reduced to ⅓.

FIG. 5 is a conceptual diagram showing vertical addition and horizontalthinning-out and addition in units of, for example, three pixels in thevertical and horizontal directions. In a case of a CCD imaging deviceincluding 1920 (vertical) by 2560 (horizontal) pixels, by way ofexample, pixel information of 640 (vertical) by 853 (horizontal) pixelsis obtained by performing vertical and horizontal pixel addition (withthe horizontal thinning-out processing) in units of three pixels. Thus,there is a good balance between the horizontal resolution and thevertical resolution of a moving image. The centroid of pixels in bothvertical and horizontal directions can also be uniform.

In particular, the charge controller 13A provided between the imagingunit 11 and the accumulator 12 allows the signal charges of verticalCCDs 112 in the columns of which pixels are to be added, e.g., thevertical CCDs 112A and 112C, to be transmitted and added in theaccumulator 12 before they are transferred to the horizontal CCD 14. Noempty packets are produced in the horizontal CCD 14 due to nothinning-out, thus preventing the occurrence of smearing caused byaddition of smear components in empty packets. That is, transfer ofcharges from the vertical CCD 112B of which pixels are to be thinned outis stopped to thin out the signal components and the smear components,thus preventing the occurrence of smearing.

In the first embodiment, in color coding based on two (horizontal) bytwo (vertical) pixel patterns, horizontal thinning-out and additionprocessing is performed in units of three columns (i.e., threehorizontal pixels) to thin out the pixel information for the middlecolumn and to add the pixel information for the side columns. Therefore,advantageously, pixel information of pixels of the same color can beadded.

In the first embodiment, in color coding based on a primary-color Bayerarray having two (horizontal) by two (vertical) pixel patterns, in unitsof three columns of the vertical CCDs 112, the pixel information for themiddle column is thinned out while the pixel information for the sidecolumns are added. However, this is merely an example, and any otherform may be used.

The color coding scheme of the color filter is not limited to colorcoding based on a primary-color Bayer array, and may be color codingbased on a primary-color stripe array, a complementary-color latticearray, or the like. The number of columns used as a unit of thinning-outand addition is not limited to three but may be four or more. The columnof which the pixel information is to be thinned out is not limited toone middle column. The column of which the pixel information is to bethinned out or the column of which the pixel information is to be addedcan be determined depending on the color coding scheme.

The pixels of which pixel information is to be added are not limited topixels of the same color. For example, pixels of different primarycolors may be added to obtain complementary-color pixel information. Inthis case, a signal processing system in the subsequent stage of the CCDimaging device 10 regenerates the original primary colors from thecomplementary color.

Still-Image Capturing Mode

Next, the operation of the charge controller 13A in the still-imagecapturing mode will be described with reference to a timing chart shownin FIG. 6.

In the first embodiment, the horizontal thinning-out and additionprocessing is performed in units of, for example, three columns (i.e.,three horizontal pixels). The charge controller 13A performs processingfor converting the signal charges transferred in parallel from the threevertical CCDs 112A, 112B, and 112C into serially arranged signal chargesand sequentially outputting the serially arranged signal charges. In thestill-image capturing mode in which the signal charges of all pixels areindependently read out, three-line sequence is used in which signalcharges of pixels in one row are read out in three blocks.

In the three-line sequence, signal charges of pixels corresponding to ⅓of the number of pixels in one row of the imaging unit 11 aresequentially transferred in each-line sequence by the charge controller13A, the accumulator 14, and the horizontal CCD 12, and are output viathe charge detecting unit 15. The total processing time of thethree-line sequence is substantially the same as the processing time ofa sequence in which signal charges of pixels in one row of the imagingunit 11 are sequentially transferred by the accumulator 14 and thehorizontal CCD 12 and are output via the charge detecting unit 15.

In the timing chart shown in FIG. 6, when the fifth-phase verticaltransfer pulse IM5 and then the sixth-phase vertical transfer pulse IM6are sequentially brought to an “H” level from an “L” level, the verticalCCDs 112 (112A, 112B, and 112C) transfer the signal charges of thepixels in the bottom row of the imaging unit 11 in parallel to thecharge controller 13A.

In units of three columns, i.e., the vertical CCDs 112A, 112B, and 112C,first, the signal charges of the vertical CCD 112A in the first columnare transferred to the accumulator 12, passing through the chargecontroller 13A. The storage pulses Storage1 and Storage2 are in the “H”level state so that the potentials under the storage electrodes 131B and131C become deep, and the hold pulses Hold1 and Hold2 are in the “L”level state so that the potentials under the hold electrodes 132B and132C become shallow. Thus, the signal charges of the vertical CCDs 112Band 112C in the second and third columns are accumulated under thestorage electrodes 131B and 131C, and potential barriers produced underthe hold electrodes 132B and 132C stop transferring charges to theaccumulator 12.

The signal charges of the vertical CCD 112A in the first columntransferred to the accumulator 12 through the charge controller 13A arevertically transferred to the horizontal CCD 14 by the four-phase (ST1to ST4) driving in the accumulator 12. In the horizontal CCD 14, thesignal charges are horizontally transferred by the two-phase (H1 and H2)driving to the charge detecting unit 15. The charge detecting unit 15converts the signal charges into voltage signals and outputs theconverted signals. The processing of the first-line sequence is nowcompleted, and then the processing of the second-line sequence isperformed.

In the second-line sequence, the hold pulse Hold1 is brought to the “H”level from the “L” level so that the potential under the hold electrode132B becomes deep, and the storage pulse Storage1 is then brought to the“L” level from the “H” level so that the potential under the storageelectrode 131B becomes shallow. Thus, the signal charges of the verticalCCD 112B in the second column held under the storage electrode 131B aretransferred to the accumulator 12, passing through the charge controller13A.

The signal charges of the vertical CCD 112C in the third column arestill held under the storage electrode 131C. The signal charges of thevertical CCD 112B in the second column transferred to the accumulator 12through the charge controller 13A are vertically transferred by theaccumulator 12 to the horizontal CCD 14. In the horizontal CCD 14, thesignal charges are horizontally transferred to the charge detecting unit15. The charge detecting unit 15 converts the signal charges intovoltage signals and outputs the converted signals. The processing of thesecond-line sequence is now completed, and then the processing of thethird-line sequence is performed.

In the third-line sequence, the hold pulse Hold2 brought to the H″ levelfrom the “L” level so that the potential under the hold electrode 132Cbecomes deep, and the storage pulse Storage2 is then brought to the “L”level from the “H” level so that the potential under the storageelectrode 131C becomes shallow. Thus, the signal charges of the verticalCCD 112C in the third column held under the storage electrode 131C aretransferred to the accumulator 12, passing through the charge controller13A.

The signal charges of the vertical CCD 112C in the third columntransferred to the accumulator 12 through the charge controller 13A arevertically transferred by the accumulator 12 to the horizontal CCD 14.In the horizontal CCD 14, the signal charges are horizontallytransferred to the by the charge detecting unit 15. The charge detectingunit 15 converts the signal charges into voltage signals, and outputsthe converted signals. The processing of the third-line sequence, thatis, the processing of the overall three-line sequence, is now completed.

As a result, as discussed above, the charge controller 13A allows thesignal charges of three pixels transferred in parallel in units of threevertical CCDs 112 of the imaging unit 11, i.e., the vertical CCDs 112A,112B, and 112C, to be converted into serially arranged signal charges,which are then sequentially transferred to the accumulator 12. The pixelsignals output after the three-line sequence are returned to theoriginal pixel array of one row of the imaging unit 11 by the signalprocessing system in the subsequent stage of the CCD imaging device 10by alternately rearranging the three-line pixel signals using a linememory or the like.

In the still-image capturing mode, therefore, signal charges transferredin parallel from the imaging unit 11 in units of, for example, threecolumns (i.e., three horizontal pixels), which are used as a unit of thehorizontal thinning-out and addition processing, are converted intoserially arranged signal charges by the charge controller 13A. Even ifthe charge controller 13A used for horizontal thinning-out and additionin the moving-image capturing mode is provided between the imaging unit11 and the accumulator 12, the signal charges of all pixels 111 of theimaging unit 11 can independently be read out by the three-linesequence.

In case of performing the horizontal thinning-out and additionprocessing in units of three columns, the charge controller 13Aaccording to the first embodiment is not provided with a storageelectrode or hold electrode for the vertical CCD 112A in the firstcolumn, and transfers the signal charges of the vertical CCD 112A in thefirst column directly to the accumulator 12. Alternatively, the chargecontroller 13A may be provided with a storage electrode and a holdelectrode for the vertical CCD 112A in the first column in a similarmanner to that of the vertical CCDs 112B and 112C in the second andthird columns, and may temporarily hold the signal charges of thevertical CCD 112A in the first column.

In this case, in either the moving-image capturing mode or thestill-image capturing mode, the timing relation may be set so that thetemporarily held signal charges of the vertical CCD 112A in the firstcolumn can first pass through the charge controller 13A. However, thestorage electrode and the hold electrode provided for the vertical CCD112A in the first column increase the complexity of the configurationand the timing control. It can be understood that no storage electrodeor hold electrode provided for the vertical CCD 112A in the first columnis more advantageous.

As discussed above, in the FIT-type CCD imaging device 10 including theimaging unit 11 and the accumulator 12, the charge controller 13Aaccording to the first embodiment is provided between the imaging unit11 and the accumulator 12. In a case where the charge controller 13Aperforms the horizontal thinning-out and addition processing in themoving-image capturing mode, the number of pixels to be added and to bethinned out in the horizontal direction can arbitrarily be set dependingon the number of pixels to be added in the vertical direction (possiblywith the thinning-out processing), thereby preventing the amount ofhorizontal image information from being excessively larger than theamount of vertical pixel information. Thus, there is a good balancebetween the horizontal resolution and the vertical resolution of amoving image. Along with the reduction in the amount of horizontal imageinformation, the horizontal driving frequency can be reduced.

In the first embodiment, pixel addition without the thinning-outprocessing is performed in the vertical direction, and no empty packetsare produced in the vertical CCDs 112. The charge controller 13A usedfor the horizontal thinning-out and addition processing further thinsout the signal components and the smear components for the vertical CCDof which pixels are to be thinned out so as not to produce empty packetsin the horizontal CCD 14. In the moving-image capturing mode, therefore,the occurrence of smearing caused by pixel addition can be prevented.

In particular, in the first embodiment, with the use of a combination ofthe FIT type that is greatly effective as a smear reduction solution andthe horizontal thinning-out and addition method performed by the chargecontroller 13A according to the first embodiment, in other words, thelight-shielded accumulator 12 mounted in the CCD imaging deviceincluding the charge controller 13A according to the first embodiment,the occurrence of smearing can greatly be reduced in the video mode incooperation with the smear reduction effect of the accumulator 12.

In a case of the FIT-type CCD imaging device 10, in the moving-imagecapturing mode, the charge controller 13A performs the horizontalthinning-out and addition processing and outputs signal charges to theaccumulator 12. In the still-image capturing mode, the charge controller13A converts the signal charges transferred in parallel from the imagingunit 11 in units of pixels to be subjected to the horizontalthinning-out and addition processing into serially arranged signalcharges, and outputs the signal charges to the accumulator 12.Therefore, the amount of pixel information in the horizontal directioncan be reduced (to ⅓ when the horizontal thinning-out and additionprocessing is carried out in units of three horizontal pixels), and thevertical size of the accumulator 12 can also be reduced.

This is because the reduction in the amount of horizontal pixelinformation allows the horizontal size of a packet in the accumulator 12to be designed to be larger than the horizontal size of a pixel unit(including a pixel 111 and a vertical CCD 112 associated therewith). Forexample, in the case of units of three horizontal pixels, the horizontalsize of the packet can be designed to be as large as the horizontal sizeof the three pixel units corresponding to three horizontal pixels. Withsuch a large horizontal size, a certain amount of charge handled by thepacket can be maintained if the vertical size of the packet is reduced,and the vertical size of the accumulator 12 can therefore be reduced.Therefore, the chip size of the CCD imaging device 10 can greatly bereduced in the vertical direction.

In a case of an FIT-type CCD imaging device of the related art, thevertical size of the accumulator 12 is generally about 50% larger thanthe vertical size of the imaging unit 11, and the chip size in thevertical direction of the CCD imaging device is about 1.5 times thevertical size of the imaging unit 11. The chip size of the CCD imagingdevice directly affects the device price. The FIT-type CCD imagingdevice is therefore too expensive to mount in a consumer imagingapparatus, e.g., a digital still camera, at the current stage.

In the FIT-type CCD imaging device 10 including the charge controller13A according to the first embodiment, on the contrary, although itdepends on the number of pixels to be added and thinned out in thehorizontal thinning-out and addition processing, the horizontal size ofa packet of the accumulator 12 can be designed to be as large as thesize of three horizontal pixels, and the vertical size of theaccumulator 12 can be reduced to about 20% of the vertical size of theimaging unit 11, for example, in a case where the horizontalthinning-out and addition processing is performed in units of threecolumns (i.e., three horizontal pixels) and one column of pixel (i.e.,one pixel) is thinned out. The chip size of the CCD imaging device 10can therefore be reduced in the vertical direction to about 1.2 timesthe vertical size of the imaging unit 11.

Accordingly, with the use of horizontal thinning-out and addition usingthe charge controller 13A, the FIT-type CCD imaging device 10 includingthe charge controller 13A according to the first embodiment allowssignificant reduction in chip size and also allows significant reductionin cost. The FIT-type CCD imaging device 10 is therefore suitable tomount in a consumer imaging apparatus, e.g., a digital still camera,which is difficult in the related art in view of cost. Moreover, withthe ability to significantly reduce the occurrence of smearing in thevideo mode in cooperation with the smear reduction effect of the FITtype, the image quality can greatly be increased.

While the first embodiment has been described as an implementation of anFIT-type CCD imaging device including the imaging unit 11 and theaccumulator 12, by way of example, the present invention is not limitedto this example. CCD imaging devices, such as IT-type CCD imagingdevices without the accumulator 12, or charge-transfer solid-stateimaging devices other than CCD imaging devices may be employed.

That is, the charge controller 13A is provided below the imaging unit11, and, in the moving-image capturing mode, the charge controller 13Aperforms the horizontal thinning-out and addition processing and outputssignal charges to the horizontal CCD 14. In the still-image capturingmode, the charge controller 13A converts the signal charges transferredin parallel from the imaging unit 11 in units of pixels to be subjectedto the horizontal thinning-out and addition processing into seriallyarranged signal charges, and outputs the signal charges to thehorizontal CCD 14. Therefore, there is a good balance between thehorizontal resolution and the vertical resolution without the occurrenceof smearing in the video mode, and the horizontal driving frequency canbe reduced.

Second Embodiment

FIG. 7 is a schematic plan pattern view showing the configuration of themain part including a charge controller 13B according to a secondembodiment of the present invention. In FIG. 7, the portions equivalentto those shown in FIG. 2 are identified by the same reference numerals.Color coding of a color filter (not shown) provided on the top layer ofthe imaging unit 11 is based on two (horizontal) by two (vertical) pixelpatterns, by way of example, and the charge controller 13B performsprocessing in units of four columns (i.e., four horizontal pixels).

In a predetermined operation mode, a plurality of columns of thevertical CCDs 112 are used as a unit, and the charge controller 13Baccording to the second embodiment stops transferring charges from avertical CCD 112 in a predetermined column of the plurality of columnsto thin out the charges, and reads out the signal charges transferredfrom the remaining vertical CCDs 112 to the accumulator 12. Thisprocessing is hereinafter referred to as horizontal thinning-out andread-out processing. In another operation mode different from thepredetermined operation mode, the charge controller 13A reads out thesignal charges transferred in parallel in units of the plurality ofcolumns from the plurality of vertical CCDs 112 using a multiple-linesequence, e.g., a two-line sequence.

Referring to FIG. 7, four vertical CCDs 112, namely, 112A, 112B, 112C,and 112D, are used as a unit. With respect to the middle two verticalCCDs 112B and 112C in the four vertical CCDs 112A, 112B, 112C, and 112D,the charge controller 13B is provided with a storage electrode 135 and ahold electrode 136 in each of the channels so as to extend across thechannels in such a manner that the storage electrode 135 is closer tothe imaging unit 11.

With respect to the side vertical CCDs 112A and 112D, the chargecontroller 13B is not provided with a storage electrode or a holdelectrode. The storage electrode 135 is partially cut out, and a drainportion 137 serving as a charge drain unit is provided in the cutoutregion of the storage electrode 135.

As discussed above, the charge controller 13B with the above-describedconfiguration is driven and controlled by the control pulses generatedby the timing generator 20, i.e., the storage pulse Storage, the drainvoltage Drain, and the hold pulse Hold, to perform the horizontalthinning-out and read-out processing.

Specifically, the storage pulse Storage is carried by a control line138-1 to drive the storage electrode 135, and the drain voltage Drain iscarried by a control line 138-2 to drive the drain portion 137. The holdpulse Hold is carried by a control line 138-3 to drive the holdelectrode 136.

For example, the control lines 138-1 to 138-3 carrying the storage pulseStorage, the drain voltage Drain, and the hold pulse Hold extend inparallel to one another across the charge controller 13B in thearrangement direction of the vertical CCDs 112 (i.e., the horizontaldirection), and have a shunt configuration such that the storageelectrode 135, the drain portion 137, and the hold electrode 136 arebrought into electrical contact for every four columns.

The charge controller 13B with the above-described configurationperforms the horizontal thinning-out and read-out processing in units offour columns (i.e., four horizontal pixels), by way of example, so as tosupport, for example, vertical two-pixel addition for every four pixels.In order to perform two-pixel addition for every four pixels in thevertical direction, the vertical CCDs 112 are driven by, for example,eight-phase vertical transfer pulses IM1 to IM8.

A method for driving the CCD imaging device 10 including the chargecontroller 13B with the above-described configuration will now bedescribed in the context of a moving-image capturing mode for capturinga moving image (including a monitoring mode) and a still-image capturingmode for capturing a still image.

Moving-Image Capturing Mode

First, the vertical pixel addition operation in the moving-imagecapturing mode will be described with reference to FIG. 8.

As an example, in a case of color coding based on a primary-color Bayerarray having two (horizontal) by two (vertical) pixel patterns,two-pixel addition in which two pixels of the same color are added forevery other pixel in units of four pixels is used, and the processingfor thinning out a pixel is not performed.

Addition of two pixels of the same color for every other pixel isperformed in the vertical direction without performing the verticalthinning-out processing, thereby allowing for uniformity of the centroidof pixels in taking a moving image, as can be seen from equal intervalsin the vertical direction between adders, indicated by typical signs inFIG. 8 for adding pixels. No thinning-out of pixel information preventsthe generation of false-color signals. In addition, since the processingfor thinning out pixel information is not performed, no empty packetsare produced during vertical transfer, thus preventing the occurrence ofsmearing.

Now, the operation of the charge controller 13B in the moving-imagecapturing mode, that is, the horizontal thinning-out and read-outoperation, will be described with reference to a timing chart shown inFIG. 9.

In the timing chart shown in FIG. 9, when the seventh-phase verticaltransfer pulse IM7 and then the eighth-phase vertical transfer pulse IM8are sequentially brought to an “H” level from an “L” level, the verticalCCDs 112 (112A, 112B, 112C, and 112D) transfer the signal charges of thepixels in the bottom row of the imaging unit 11 to the charge controller13B. In units of four columns, i.e., the vertical CCDs 112A, 112B, 112C,and 112D, the signal charges of the vertical CCDs 112A and 112D in thefirst and fourth columns are transferred to the accumulator 12, passingthrough the charge controller 13B.

The storage pulse Storage is in the “H” level state so that thepotential under the storage electrode 135 becomes deep, and the holdpulse Hold is in the “L” level state so that the potential under thehold electrode 136 becomes shallow. Thus, the signal charges of thevertical CCDs 112B and 112C in the second and third columns areaccumulated under the storage electrode 135, and a potential barrierproduced under the hold electrode 136 stops transferring these signalcharges to the accumulator 12. The potential barrier stops transferringnot only the signal components (i.e., the signal charges) but also smearcomponents (or smear charges). The accumulated charges over thepotential barrier are drained to the drain portion 137 by the followingvertical transfer operation.

Accordingly, in a case where horizontal thinning-out and read-outprocessing is performed in units of four columns, i.e., the verticalCCDs 112A, 112B, 112C, and 112D, the charge controller 13B stopstransferring the signal charges of the middle vertical CCDs 112B and112C, and transmits the signal charges of the side vertical CCDs 112Aand 112D so that the transmitted signal charges are temporarilyaccumulated in the accumulator 12. In the moving-image capturing mode,therefore, the charge controller 13B allows the horizontal thinning-outand read-out processing for thinning out the pixel information(including the smear components) of the two middle columns (i.e., twopixels) and reading out the pixel information for the side columns.

The signal charges that are obtained by the charge controller 13Bperforming thinning-out to, for example, ½ of the number of horizontalpixels are vertically transferred to the horizontal CCD 14 by thefour-phase (ST1 to ST4) driving in the accumulator 12. In the horizontalCCD 14, the signal charges are horizontally transferred by the two-phase(H1 and H2) driving to the charge detecting unit 15. The chargedetecting unit 15 converts the signal charges into voltage signals andoutputs the converted signals.

In the capturing operation in the moving-image capturing mode,therefore, the horizontal thinning-out and read-out processing isperformed, and the number of pixels to be thinned out can arbitrarily beset depending on the number of pixels to be added for vertical pixeladdition to prevent the amount of vertical pixel information from beingexcessively larger than the amount of horizontal image information andto allow the same rate of pixel information in both directions.Therefore, there is a good balance between the horizontal resolution andthe vertical resolution of a moving image. In the case of the secondembodiment, in association with vertical two-pixel addition for everyfour pixels, two pixels are thinned out for every four horizontalpixels. The amount of pixel information in the vertical and horizontaldirections is therefore reduced to ½.

In particular, the charge controller 13B provided between the imagingunit 11 and the accumulator 12 allows the signal charges of the verticalCCDs 112 in the columns of which pixels are read out, e.g., the verticalCCDs 112A and 112D, to be transmitted and temporarily accumulated in theaccumulator 12 before they are transferred to the horizontal CCD 14. Noempty packets are produced in the horizontal CCD 14 due to nothinning-out, thus preventing the occurrence of smearing caused byaddition of smear components in empty packets. That is, transfer ofcharges from the vertical CCDs 112B and 112C of which pixels are to bethinned out is stopped to thin out the signal components and the smearcomponents, thus preventing the occurrence of smearing.

In the second embodiment, in color coding based on a primary-color Bayerarray having two (horizontal) by two (vertical) pixel patterns, in unitsof four columns of the vertical CCDs 112, the pixel information for thetwo middle columns is thinned out while the pixel information for theside columns are read out. However, this is merely an example, and anyother form may be used.

The color coding scheme of the color filter is not limited to colorcoding based on a primary-color Bayer array, and may be color codingbased on a primary-color stripe array, a complementary-color latticearray, or the like. The number of columns as a unit of thinning-out andread-out is not limited to four but may be five or more. The columns ofwhich the pixel information is to be thinned out is not limited to twomiddle columns. The columns of which the pixel information is to bethinned out can be determined depending on the color coding scheme.

Still-Image Capturing Mode

Next, the operation of the charge controller 13B in the still-imagecapturing mode will be described with reference to a timing chart shownin FIG. 10.

In the second embodiment, the horizontal thinning-out and read-outprocessing is performed in units of, for example, four columns (i.e.,four horizontal pixels). The charge controller 13B performs processingfor reading out the signal charges transferred in parallel from the fourvertical CCDs 112A, 112B, 112C, and 112D in two blocks. In thestill-image capturing mode in which signal charges of all pixels areindependently read out, two-line sequence is used in which signalcharges of pixels in one row are read out in two blocks.

In the two-line sequence, signal charges of pixels corresponding to ½ ofthe number of pixels in one row of the imaging unit 11 are sequentiallytransferred in each-line sequence by the charge controller 13B, theaccumulator 14, and the horizontal CCD 12, and are output via the chargedetecting unit 15. The total processing time of the two-line sequence issubstantially the same as the processing time of a sequence in whichsignal charges of pixels in one row of the imaging unit 11 aresequentially transferred by the accumulator 12 and the horizontal CCD 14and are output via the charge detecting unit 15.

In the timing chart shown in FIG. 10, when the seventh-phase verticaltransfer pulse IM7 and then the eighth-phase vertical transfer pulse IM8are sequentially brought to an “H” level from an “L” level, the verticalCCDs 112 (112A, 112B, 112C, and 112D) transfer the signal charges of thepixels in the bottom row of the imaging unit 11 in parallel to thecharge controller 13B.

In units of four columns, i.e., the vertical CCDs 112A, 112B, 112C, and112D, first, the signal charges of the vertical CCDs 112A and 112D inthe first and fourth columns are transferred to the accumulator 12,passing through the charge controller 13B. The storage pulse Storage isin the “H” level state so that the potential under the storage electrode135 becomes deep, and the hold pulse Hold is in the “L” level state sothat the potential under the hold electrode 136 becomes shallow. Thus,the signal charges of the vertical CCDs 112B and 112C in the second andthird columns are accumulated under the storage electrode 135, and apotential barrier produced under the hold electrode 136 stopstransferring charges to the accumulator 12.

The signal charges of the vertical CCDs 112A and 112D in the first andfourth columns transferred to the accumulator 12 through the chargecontroller 13B are vertically transferred to the horizontal CCD 14 bythe four-phase (ST1 to ST4) driving in the accumulator 12. In thehorizontal CCD 14, the signal charges are horizontally transferred bythe two-phase (H1 and H2) driving to the charge detecting unit 15. Thecharge detecting unit 15 converts the signal charges into voltagesignals and outputs the converted signals. The processing of thefirst-line sequence is now completed, and then the processing of thesecond-line sequence is performed.

In the second-line sequence, the hold pulse Hold is brought to the “H”level from the “L” level so that the potential under the hold electrode136 becomes deep, and the storage pulse Storage is then brought to the“L” level from the “H” level so that the potential under the storageelectrode 135 becomes shallow. Thus, the signal charges of the verticalCCDs 112B and 112C in the second and third columns held under thestorage electrode 135 are transferred to the accumulator 12, passingthrough the charge controller 13B.

The signal charges of the vertical CCDs 112B and 112C in the second andthird columns transferred to the accumulator 12 through the chargecontroller 13B are vertically transferred by the accumulator 12 to thehorizontal CCD 14. In the horizontal CCD 14, the signal charges arehorizontally transferred to the by the charge detecting unit 15. Thecharge detecting unit 15 converts the signal charges into voltagesignals and outputs the converted signals. The processing of thesecond-line sequence, that is, the processing of the overall two-linesequence, is now completed.

As a result, as discussed above, the charge controller 13B allows thesignal charges of four pixels transferred in parallel in units of fourvertical CCDs 112 of the imaging unit 11, i.e., the vertical CCDs 112A,112B, 112C, and 112D, to be read out in two blocks, which are thensequentially transferred to the accumulator 12. The pixel signals outputafter the two-line sequence are returned to the original pixel array ofone row of the imaging unit 11 by the signal processing system in thesubsequent stage of the CCD imaging device 10 by rearranging thetwo-line pixel signals using a line memory or the like.

In the still-image capturing mode, therefore, signal charges transferredin parallel from the imaging unit 11 in units of, for example, fourcolumns (i.e., four horizontal pixels), which are used as a unit of thehorizontal thinning-out and read-out processing, are read out in aplurality of blocks (in this example, two blocks) by the chargecontroller 13B. Even if the charge controller 13B used for thehorizontal thinning-out and read-out processing in the moving-imagecapturing mode is provided between the imaging unit 11 and theaccumulator 12, the signal charges of all pixels 111 of the imaging unit11 can independently be read out by the two-line sequence.

As discussed above, in the FIT-type CCD imaging device 10 including theimaging unit 11 and the accumulator 12, the charge controller 13Baccording to the second embodiment is provided between the imaging unit11 and the accumulator 12. In a case where the charge controller 13Bperforms the horizontal thinning-out and read-out processing in themoving-image capturing mode, the number of pixels to be thinned out inthe horizontal direction can arbitrarily be set depending on the numberof pixels to be added in the vertical direction (possibly with thethinning-out processing), thereby preventing the amount of horizontalimage information from being excessively larger than the amount ofvertical pixel information. Thus, there is a good balance between thehorizontal resolution and the vertical resolution of a moving image.Along with the reduction in the amount of horizontal image information,the horizontal driving frequency can be reduced.

In the second embodiment, pixel addition without the thinning-outprocessing is performed in the vertical direction, and no empty packetsare produced in the vertical CCDs 112. The charge controller 13B usedfor the horizontal thinning-out and read-out processing further thinsout the signal components and the smear components for the vertical CCDof which pixels are to be thinned out so as not to produce empty packetsin the horizontal CCD 14. In the moving-image capturing mode, therefore,the occurrence of smearing caused by thinning-out and read-out can beprevented.

In particular, in the second embodiment, with the use of a combinationof the FIT type that is greatly effective as a smear reduction solutionand the horizontal thinning-out and read-out method performed by thecharge controller 13B according to the second embodiment, in otherwords, the light-shielded accumulator 12 mounted in the CCD imagingdevice including the charge controller 13B according to the secondembodiment, the occurrence of smearing can greatly be reduced in thevideo mode in cooperation with the smear reduction effect of theaccumulator 12.

In a case of the FIT-type CCD imaging device 10, in the moving-imagecapturing mode, the charge controller 13B performs the horizontalthinning-out and read-out processing and outputs signal charges to theaccumulator 12. In the still-image capturing mode, the charge controller13B divides the signal charges transferred in parallel from the imagingunit 11 in units of pixels to be subjected to the horizontalthinning-out and read-out processing into a plurality of blocks, andoutputs the plurality of blocks of signal charges to the accumulator 12.Therefore, the amount of pixel information in the horizontal directionis reduced (to ½ when the horizontal thinning-out and read-outprocessing is carried out in units of four horizontal pixels), and thevertical size of the accumulator 12 is reduced to about 20% of thevertical size of the imaging unit 11. The chip size of the CCD imagingdevice 10 can therefore be reduced in the vertical direction to about1.2 times the vertical size of the imaging unit 11. The reasons for thesize reduction are the same as those in the first embodiment.

Accordingly, with the use of horizontal thinning-out and read-out usingthe charge controller 13B, the FIT-type CCD imaging device 10 includingthe charge controller 13B according to the second embodiment allowssignificant reduction in chip size and also allows significant reductionin cost. The FIT-type CCD imaging device 10 is therefore suitable tomount in a consumer imaging apparatus, e.g., a digital still camera,which is difficult in the related art in view of cost. Moreover, withthe ability to significantly reduce the occurrence of smearing in thevideo mode in cooperation with the smear reduction effect of the FITtype, the image quality can greatly be increased.

Application Examples

The FIT-type CCD imaging device 10 including the above-described chargecontroller 13A or 13B according to the first or second embodiment issuitable to mount as an imaging device in an imaging apparatus (cameramodule), particularly, a consumer imaging apparatus, e.g., a digitalstill camera.

FIG. 11 is a block diagram of an imaging apparatus (e.g., a digitalstill camera) according to an embodiment of the present invention inwhich the FIT-type CCD imaging device 10 including the charge controller13A or 13B according to the first or second embodiment is mounted as animaging device.

Referring to FIG. 11, the imaging apparatus according to the presentembodiment includes an imaging device 31, a driving circuit 32 thatdrives the imaging device 31, a lens 33 that focuses incident light(image light) from an object (not shown) onto an imaging surface of theimaging device 31, a signal processing circuit 34 that processes anoutput signal of the imaging device 31, an image recording device 35that records an image signal processed by the signal processing circuit34 onto a recording medium, an image display device 36 that displays theimage signal processed by the signal processing circuit 34 on a monitor,and a mode setting unit 37 that sets the capturing mode of the imagingdevice 31.

In the imaging apparatus with the above-described configuration, theimaging device 31 may be the FIT-type CCD imaging device 10 includingthe above-described charge controller 13A or 13B according to the firstor second embodiment. The driving circuit 32 has the function of thetiming generator 20 shown in FIG. 1. Incident light (image light) fromthe object is focused on the imaging surface of the imaging device 31via an optical system including the lens 33. The mode of the imagingdevice 31 is set by the user using the mode setting unit 37 between amoving-image capturing mode (a first capturing mode) for capturing amoving image and a still-image capturing mode (a second capturing mode)for capturing a still image.

When the moving-image capturing mode (including the monitoring mode) isset by the mode setting unit 36, the driving circuit 32 generates thetiming signals at the timing shown in the timing chart of FIG. 4 or 9.When the still-image capturing mode is set by the mode setting unit 36,the driving circuit 32 generates the timing signals at the timing shownin the timing chart of FIG. 6 or 10. The imaging device 31 is driven andcontrolled by the generated timing signals.

The signal processing circuit 34 performs signal processing on an outputsignal of the imaging device 31, such as correlated double sampling(CDS) and analog-to-digital (A/D) conversion. In the still-imagecapturing mode, the signal processing circuit 34 rearranges three-lineor two-line pixel signals output by the three-line sequence (the firstembodiment) or the two-line sequence (the second embodiment) from theimaging device 31 using, for example, a line memory.

In the still-image capturing mode, the image recording device 35 recordsthe image signal processed by the signal processing circuit onto arecording medium. The image information recorded on the recording mediumis hard-copied using a printer or the like. In the moving-imagecapturing mode, the image display device 35 displays the image signalprocessed by the signal processing circuit 34 on a display monitor suchas a liquid crystal display.

As discussed above, in a case where the FIT-type CCD imaging device 10(as described in the first embodiment) is mounted as the imaging device31 in an imaging apparatus such as a digital still camera, the CCDimaging device 10 allows significant reduction of the occurrence ofsmearing in the video mode and allows reduction in chip size and cost. Alow-cost high-quality imaging apparatus with reduction of the occurrenceof smearing can therefore be achieved.

In recent imaging apparatuses, such as digital still cameras, demandsfor higher density cells (or unit pixels) for the purpose of high stillimage quality have increased, and, due to the characteristics of CCDimaging devices, the higher density cells can increase the occurrence ofsmearing. It is therefore effective to mount the low-cost CCD imagingdevice 10 with great reduction of the occurrence of smearing in thevideo mode as an imaging device, particularly, in such imagingapparatuses.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A solid-state imaging device comprising: an imaging unit including aplurality of pixels arranged into a matrix for performing photoelectricconversion and a plurality of vertical transfer units arranged incolumns for vertically transferring signal charges of the plurality ofpixels on a column-by-column basis; a charge control unit that uses apredetermined number of columns greater than one as a unit in apredetermined operation mode and that, in the predetermined operationmode, performs processing to stop transferring charges from a verticaltransfer unit in a predetermined column of the predetermined number ofcolumns and to transmit the signal charges transferred from the verticaltransfer units in the remaining columns of the predetermined number ofcolumns; an accumulation unit that temporarily accumulates the signalcharges output from the charge control unit; and a horizontal transferunit that horizontally transfers the signal charges output from theaccumulation unit, wherein, the accumulation unit is provided in unitsof the predetermined number of columns.
 2. A method for driving asolid-state imaging device including an imaging unit including aplurality of pixels arranged into a matrix for performing photoelectricconversion and a plurality of vertical transfer units arranged incolumns for vertically transferring signal charges of the plurality ofpixels on a column-by-column basis, an accumulation unit for temporarilyaccumulating the signal charges transferred from the plurality ofvertical transfer units, and a horizontal transfer unit for horizontallytransferring the signal charges output from the accumulation unit, themethod comprising the step of: in a predetermined operation mode, inwhich a predetermined number of columns greater than one is used as aunit, performing processing in the predetermined operation mode to stoptransferring charges from a vertical transfer unit in a predeterminedcolumn of the predetermined number of columns and to transmit the signalcharges transferred from the vertical transfer units in the remainingcolumns of the predetermined number of columns to output the transmittedsignal charges to the accumulation unit.